The present invention generally relates a to recording paper length sensing apparatus, and more particularly to a recording paper length sensing apparatus which automatically senses a length of recording paper in the form of a cut sheet used by an image forming apparatus such as a printer, a facsimile or the like.
Conventional image forming apparatuses such as a printer, a facsimile or the like, ordinarily employ recording paper in the form of a cut sheet together with a number of paper cassettes which can accommodate many sheets of the recording paper. These paper cassettes have a specific fixed size in accordance with the respective sizes of recording paper in which an image is recorded by the image forming apparatus. Before using the image forming apparatus, an operator must select a paper cassette having an appropriate size, which is in accordance with that of recording paper to be used, from among those paper cassettes and must mount the selected paper cassette into the image forming apparatus. Therefore, the above described image forming apparatus which uses the paper cassette having a size appropriate for that of recording paper requires a number of paper feed inlets to which several paper cassettes are mounted for different recording paper sizes and requires a number of paper feeding mechanisms for supplying paper from the paper cassette to an image forming mechanism within the image forming apparatus. To meet these requirements fully, it is unavoidable that the size of image forming apparatus becomes great and the manufacturing cost thereof becomes high. And, with the paper cassettes being used in the image forming apparatus, it is difficult to make use of recording paper which has a size different from those sizes of regular paper and, in the case of the above described image forming apparatus which uses the paper cassette having a specific fixed size, a user often experiences difficulty in using a recording paper which has a size different from standard paper sizes which are predetermined with the paper cassettes, for example, A4 size, B4 size, Letter size or the like.